An Equal Opportunity Provider and Employer

CENTER FOR VETERINARY BIOLOGICS NOTICE 18-07

TO: Biologics Licensees, Permittees, and Applicants

Directors, Center for Veterinary Biologics

Veterinary Services Leadership Team

FROM: Byron Rippke

Director

SUBJECT: Digital Signatures on Microsoft Word Documents

I. PURPOSE

This Notice informs licensees, permittees, and applicants of a situation with 

Microsoft Word documents previously signed by CVB employees, which causes the 

digital signature to appear eventually with a “Revoked Certificate” message even 

though a valid signature was applied at the time of signing. 

II. BACKGROUND

The Center for Veterinary Biologics recently began accepting, via the NCAH Portal,

Outlines of Production and labels in Microsoft Word format (.docx). CVB 

employees digitally sign these documents when they are approved. The CVB 

utilizes an advanced electronic signature based on XAdES, which has the following 

features: 

• uniquely linked to, and capable of identifying, the signatory;

• only the signatory has control of the data used for the signature creation;

• can be identified if data attached to the signature have been changed after 

signing.

Signatures applied prior to approximately May 2, 2018, are compliant with the 

XAdES-EPES (Basic) standard, which is insufficient to ensure long-term validity of 

the signature. Signatures applied since approximately May 2, 2018, are compliant 

with the XAdES-X-L standard, which was intended to provide long-term certificate 

validation. Unfortunately, issues remain because of how the signing credentials of 

CVB employees are handled upon renewal or when an employee separates from 

Federal service. The certificates are “revoked”, which causes MS Word to display a 

“Revoked Certificate” message above the signature, even though the signature was 

valid at the time of signing. The signing certificates of most CVB employees have 

expired or will be expiring over the next several months, which will cause the 

revoked certificate message to appear on all digitally signed MS Word documents 

after the signing certificate used to apply the signature is replaced.

Animal and Plant

Health Inspection

Service

Veterinary Services

Center for Veterinary 

Biologics

1920 Dayton Avenue

PO Box 844

Ames, IA 50010

(515) 337-6100
CENTER FOR VETERINARY BIOLOGICS NOTICE 18-07

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 An Equal Opportunity Provider and Employer

After the signing certificate used to apply the signature is revoked, document signatures 

have this appearance:

Note that the signature date no longer 

displays next to the signature.

III. ACTION

The CVB continues to look into this issue and is working toward a solution. 

Readers can look at “Signature Details” to verify the original signature date and 

determine that the signature was applied while the certificate was valid. Stepwise 

instructions to drill into Signature Details are available at https://support.office.com/enus/article/view-digital-signature-and-certificate-details-76ba00cb-1e58-42aa-8717-

0caee76bb3cf.

This traceability will be sufficient for regulatory purposes with APHIS; no further 

remedial action is needed. If additional assurances of validity are required for specific 

documentation used for international registration, contact your CVB reviewer to discuss 
CENTER FOR VETERINARY BIOLOGICS NOTICE 18-07

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 An Equal Opportunity Provider and Employer

necessary actions on a case-by-case basis. For any other questions regarding digital 

signatures, contact CVB.PIMS@aphis.usda.gov

IV. IMPLEMENTATION/ APPLICABILITY

This action is effective immediately and applies to all electronically submitted Outlines 

and labels (.docx format). Adobe Acrobat documents (.pdf) are not affected.